service-worker.js

const CACHE_NAME = 'nmamit-cache-v1';
const urlsToCache = [
    './',
    './index.html',
    './img/favicon.ico',
    './img/apple-touch-icon.png',
    './img/android-chrome-192x192.png',
    './img/android-chrome-512x512.png',
    './img/logo.png',
    './site.webmanifest'
];

self.addEventListener('install', (event) => {
    event.waitUntil(
        caches.open(CACHE_NAME)
            .then((cache) => {
                return cache.addAll(urlsToCache);
            })
    );
});

self.addEventListener('fetch', (event) => {
    // Skip chrome-extension requests
    if (event.request.url.startsWith('chrome-extension://')) {
        return;
    }

    event.respondWith(
        caches.match(event.request)
            .then((response) => {
                // Cache hit - return response
                if (response) {
                    return response;
                }

                return fetch(event.request).then(
                    (response) => {
                        // Check if we received a valid response
                        if (!response || response.status !== 200 || response.type !== 'basic') {
                            return response;
                        }

                        // Clone the response
                        const responseToCache = response.clone();

                        caches.open(CACHE_NAME)
                            .then((cache) => {
                                if (event.request.url.startsWith('http')) {
                                    cache.put(event.request, responseToCache);
                                }
                            });

                        return response;
                    }
                );
            })
    );
});

self.addEventListener('activate', (event) => {
    const cacheWhitelist = [CACHE_NAME];
    event.waitUntil(
        caches.keys().then((cacheNames) => {
            return Promise.all(
                cacheNames.map((cacheName) => {
                    if (cacheWhitelist.indexOf(cacheName) === -1) {
                        return caches.delete(cacheName);
                    }
                })
            );
        })
    );
});